Posterior Descemet Research Articles

Posterior polymorphous dystrophy, case report and literature review

Case reportPosterior polymorphous dystrophy (DPP) is a rare posterior corneal dystrophy that is genetically transmitted as autosomal dominant. Corneal structures affected in this dystrophy are Descemet membrane and the endothelium. A case is presented on a 47-year-old woman with no relevant history, with typical findings of DPP (vesicular and band lesions at the endothelium and posterior Descemet). DiscussionTo our knowledge there are no reported cases of DPP in Latin-American patients in the literature. The clinical manifestations in our patient were found to be very similar to the cases reported in other populations.

Distrofia polimorfa posterior, presentación de un caso y análisis de la literatura

Case reportPosterior Polymorphous Dystrophy (DPP) is a rare posterior corneal dystrophy that is genetically transmitted as autosomal dominant. Corneal structures affected in this dystrophy are Descemet membrane and the endothelium. A case is presented on a 47 years old woman with no relevant history, with typical findings of DPP (vesicular and band lesions at the endothelium and posterior Descemet). DiscussionTo our knowledge there are no reported cases of DPP in Latin-American patients in the literature. The clinical manifestations in our patient were found to be very similar to the cases reported in other populations.

Fuchs Corneal Dystrophy: Aberrant Collagen Distribution in an L450W Mutant of theCOL8A2Gene

To characterize histologically Descemet's membrane in an early-onset Fuchs corneal dystrophy (FCD) COL8A2 mutant and compare these findings with corneas from late-onset FCD and normal corneas. A corneal explant from a patient with the L450W COL8A2 mutation and others with late-onset disease were studied with antibodies to collagens IV, VIIIA1, VIIIA2, fibronectin, and laminin. Transmission electron microscopy was performed on a portion of the explant. Control explants included eye bank corneas without known disease and surgical explants from unrelated conditions. In normal corneas, a regular array of colocalized COL8A1 and COL8A2 was observed in the anterior half of Descemet's membrane. In the L450W mutant, Descemet's membrane was several times thicker than normal and traversed by refractile strands and blebs that stained intensely for COL8A2, a feature also observed in late-onset FCD. Both the alpha1 and alpha2 subtypes of collagen VIII were observed at high levels along the anterior edge of Descemet's, another abnormal feature also found in late-onset FCD. Ultrastructure of the L450W cornea revealed a well-formed anterior banded layer more than three times thicker than normal. An unusual, thin internal layer was rich in patches of wide-spaced collagen. The layer is a distinctive pathologic structure that is associated with FCD and is characterized by approximately 120 nm periodicity and the presence of collagen VIII. Depositions of collagen IV, fibronectin, and laminin were also greatly increased in the of posterior Descemet's membrane, yet another general feature shared between early- and late-onset disease. Early-onset COL8A2 L450W disease involves massive accumulation and abnormal assembly of collagen VIII within Descemet's membrane, a process that is presumed to begin during fetal development. Both early- and late-onset subtypes of FCD appear to be the result of abnormal basement membrane assembly rather than a primary defect in endothelial metabolism.

Corneal Endothelial Involvement in Pseudoexfoliation Syndrome

Information on corneal manifestation in pseudoexfoliation syndrome is restricted to specular microscopic studies. We investigated morphologic changes of the posterior cornea of two corneal buttons with Fuchs' endothelial dystrophy obtained at penetrating keratoplasty and of one enucleated glaucomatous eye from three patients with ocular pseudoexfoliation syndrome. By transmission electron microscopy, large clumps of typical pseudoexfoliation material were found adhering to the corneal endothelium and masses of pseudoexfoliation material were incorporated into the posterior Descemet's membrane. In the affected areas, the endothelial layer appeared irregular and discontinuous, with loosely adherent, degenerating cells producing pseudoexfoliation fibers and fibroblastic cells spreading to cover denuded Descemet's membrane. The present findings indicate that the pseudoexfoliation material is initially formed by degenerative endothelial cells and that it becomes subsequently buried by overgrowing cells. The corneal endothelial involvement may potentiate complications of cataract surgery and open angle glaucoma in patients with pseudoexfoliation syndrome.

Binding of peanut agglutinin on fresh and organ-cultured porcine corneal tissue.

To investigate the binding of peanut-agglutinin (PNA) on porcine corneal tissue, several methods of tissue processing were used. In cryostat sections of postmortem tissue, PNA labeling of epithelial cell membranes was detected. In the stroma, a fibrillar structure parallel to the corneal surface was found. The anterior part of Descemet's membrane was strongly positive, whereas the posterior Descemet membrane was negative. The endothelium was faintly positive. After 3 days of organ culture, the epithelial and endothelial staining patterns were not significantly changed. The stromal fibrils detected by PNA staining showed a considerable spatial disarrangement due to the stromal hydration.

Histologic Study of a Pair of Human Corneas After Anterior Radial Keratotomy

Two corneas were obtained from a man who underwent anterior radial keratotomy in both eyes less than three months before his death. The corneas were obtained and fixed 16 hours after death and prepared for histologic evaluation four days later. Both corneas showed epithelial ingrowth in the surgical wounds, epithelial inclusion cysts in some areas, and ridges or protrusions of the posterior cornea beneath the incisions. The incisions ranged in depth from 48% to 63% of the full thickness of the cornea in the right eye and from 69% to 98% in the left eye, demonstrating the difficulties involved in maintaining a precise and predictable depth of incision, which may, in turn, be related to variations in visual results. Signs of endothelial stress, in the form of collagen and fibrils on the posterior Descemet's membrane, apparently predated the refractive surgery. Precautions such as specular microscopy may be needed to rule out this kind of surgery in patients with the early signs of some types of potential corneal disease.